Time Sieve + Myr Battlesphere + Soulherder + Yarok, the Desecrated

Time Sieve

Myr Battlesphere

Soulherder

Yarok, the Desecrated

How it works

1. At the beginning of your end step, Soulherder's second ability triggers, blinking Myr Battlesphere.
2. Myr Battlesphere's first ability triggers twice and Soulherder's first ability triggers.
3. Resolve the Soulherder trigger, putting a +1/+1 counter on it.
4. Resolve both Myr Battlesphere triggers, creating eight 1/1 Myr artifact creature tokens.
5. Activate Time Sieve by tapping it and sacrificing five Myrs, causing you to take an extra turn after this one.
6. Repeat each turn.